This application claims priority of Korea patent Application No. 10-2000-0070244, filed on Nov. 24, 2000.
(a) Field of the Invention
The present invention relates to diesel engines, and more particularly, to a method and a system for reducing turbo-lag in diesel engines and thereby increasing engine power.
(b) Description of the Related Art
Generally, a diesel engine is a compression ignition type engine in which highly pressurized fuel is directly injected into a cylinder, and the injected fuel is ignited at a high temperature caused by high compression pressure.
The diesel engine is equipped with a turbocharger which increases the mass of air delivered to the engine combustion chambers to improve engine power and reduce general exhaust gas emissions. However, in this case, the temperature of the combustion chamber rises to a high level and the production of NOx emissions increases.
Recently, to solve the above problems and stably improve engine power, a TCI (turbocharger intercooler) diesel engine has come into use, the intercooler lowering the temperature of the combustion chamber.
In a vehicle using the above diesel engine, if a driver depresses an accelerator pedal to start movement of a vehicle stopped on an uphill slope, fuel injected into the combustion chamber is imperfectly burned, and therefore visible smoke occurs.
Because the diesel engine is a spread ignition type, the mixing state of air and fuel is important, and in the case of a low air-fuel ratio, visible smoke is exhausted. Therefore, when accelerating from a stop rapidly or starting to move a vehicle stopped on an uphill slope, an amount of injected fuel should be decreased. Specially, the TCI diesel engine has a xe2x80x98turbo-lagxe2x80x99 phenomenon in that it takes a certain period of time before the engine speed increases after depressing the accelerator pedal, and therefore engine torque when starting movement is much less than that at full load of the engine. Here, if an amount of fuel injected into the combustion chamber increases, visible smoke occurs.
When starting movement of a vehicle with a TCI diesel engine rapidly or starting a vehicle stopped on an uphill slope, smoke is a factor that limits an increase of injected fuel, so the amount of injected fuel should be restricted regardless of full load power desired. The amount of injected fuel should then be increased to raise engine torque under acceleration, and the amount of air should be increased to correspond to the increase in the amount of injected fuel.
Therefore, to accelerate a vehicle rapidly from a stop or start movement of a vehicle stopped on an uphill slope, the engine idle speed is initially increased, or control for reducing gear-shift shock is eliminated in spite of much visible smoke, or inertia of a fly wheel is increased.
However, the above prior art can""t remove the turbo-lag phenomenon of the TCI diesel engine. Moreover, when the engine idle speed is increased to reduce an influence of turbo-lag without replacing vehicle hardware, noise and fuel consumption increase considerably, and when the control for reducing the gear-shift shock is eliminated, the vehicle starts rapidly even on level land with a corresponding increase in smoke, and when the inertia of the fly wheel is increased, components related to the fly wheel should be replaced.
The present invention has been made in an effort to solve the above problems. It is an object of the present invention to reduce turbo-lag in diesel engine vehicles so that engine power is increased.
A system for running a diesel engine according to the present invention comprises an idle speedup switch, an uphill slope sensor, an accelerator pedal sensor, control means increasing an idle speed to a predetermined level higher than a given idle speed such that an amount of air supply increases and outputting a driving signal in accordance with the increased amount of air supply when the idle speedup switch is on or the accelerator pedal is depressed to start a vehicle stopped on an uphill slope in an idle state, and a turbocharger providing air to the engine. Furthermore, the system according to the present invention comprises a fuel injector that injects fuel to the engine.
Also, the present invention provides a method for running the engine, the method comprising the steps of determining whether the idle speedup switch is on in the idle state, determining whether the vehicle is stopped on an uphill slope in the idle state, increasing an idle speed to the predetermined level higher than the given idle speed such that an amount of air supply increases if the accelerator pedal is depressed when the vehicle is stopped on an uphill slope or the idle speedup switch is on in the idle state, and operating the engine by injecting fuel corresponding to the increased amount of air into the combustion chamber.